Compositions and Methods for Modified Ester-Curatives and Reduction of Formaldehyde Emission and Odor in Ester-Cured Phenolic Binder Systems

ABSTRACT

This invention relates to compositions and methods for reduction of formaldehyde odor and emission during the production and curing of cores and molds, particularly those cores and molds of the foundry industry which comprise ester curable phenolic binders. More specifically, included herein is an ester-curative comprising an ester and resorcinol which, when provided in a composition with a resin and an aggregate, effectively scavenges unreacted formaldehyde thereby reducing emission and odor of the same from the composition.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 14/975,471 filed on Dec. 18, 2015.

FIELD OF THE INVENTION

This invention relates to no-bake cores and molds used in the foundryindustry. More specifically, this invention relates to modifiedester-curatives and methods for reduction of formaldehyde odor andemission during the production of cores and molds comprising estercurable phenolic binders.

BACKGROUND OF THE INVENTION

In foundry art, cores and molds for making metal castings are normallyprepared from a mixture of an aggregate material, such as sand, and abinding amount of a binder or binder system. Typically, after theaggregate material and binder have been mixed, the resulting mixture isrammed, blown, or otherwise formed to the desired shape or pattern ofthe core or mold, and then cured to a solid using a catalyst, aco-reactant, and/or heat.

One group of processes which do not require heating in order to achievecuring of the cores and molds are referred to as no-bake processes. Insuch processes, the binder components are coated on an aggregatematerial during a mixing step, and then formed around the cope and draghalves of a mold. The binder components cure after a finite period oftime, thus hardening the aggregate mixture in preparation for pouring ofmetals during casting. The elimination of the heating step has,historically, resulted in a reduction of costs in no-bake processes ascompared to earlier technologies.

Several types of no-bake binders are known. Furan no-bake (FNB) binderswere introduced as early as the 1950s. Furan binders are generallyregarded as the first genuine no-bake binders, and they are generallyeasy to control and have excellent strength. However, FNBs must contendwith significant raw material price swings, production limitations, andthe disagreeable smell of sulfur dioxide emissions during the castingprocess. Phenolic-urethane no-bake (PUNB) binders have been around sincethe 1970s, and these binders enhanced the ease of mold (aggregate)reclamation and use of no-bake binder systems in high speed productionof metal castings. However, a primary drawback of PUNBs is thecomparatively high levels of odor and smoke at molding and casting dueto the presence of solvents comprising volatile organic compounds.Organic ester-cured alkaline phenolic no-bake binders, meanwhile, wereintroduced in the early 1980s. These binder systems employ water solubleresins that have comparatively lower levels of odor emission andtoxicity during molding and casting, resulting in better workingconditions and increased foundry productivity.

Commonly used resins in ester-cured alkaline phenolic no-bake bindersystems include phenol-formaldehyde polymer. As a result, despite thecomparatively lower odor production of these systems, free formaldehydeis emitted during the molding and core making processes that use thissystem. As a gas, formaldehyde has a pungent, offensive odor. TheOccupational Safety & Health Administration (OSHA) has establishedpermissible exposure limits for the substance. Additionally,formaldehyde can cause irritation and burning of the eyes and nose ofpeople exposed to it, such foundry workers. Thus, adequate control orelimination of formaldehyde emission during the use of ester-curedalkaline phenolic no-bake binder systems is desirable.

United States Patent Publication Number 2005/0250872 to Fox et al.teaches a process comprising adding a mixture of an aqueous alkalinephenolic resole resin and a liquid organic ester for the purpose ofimmobilizing large swaths of an aggregate, such as sand in a desert. Foxet al. further discloses that urea may be added to the resin as ascavenger that reacts with unreacted formaldehyde to allegedly removeodor caused by the same.

U.S. Pat. No. 6,559,203 to Hutchings et al., teaches a combination offuran binders and resorcinol in foundry molds. Hutchings et al. furtherteaches a combination of ester cured phenolic resole resin binders andresorcinol to demonstrate general improvement in long-term tensilestrengths and humidity resistance of foundry cores made with theaforementioned binders.

It is notable that urea has been used in the prior art to reduceformaldehyde emissions. However, it can only be added in limitedamounts, as it is a source of nitrogen so the level needs to becontrolled in steel castings to avoid nitrogen related defects.Accordingly, the amounts of urea currently used are not adequate toeffectively reduce formaldehyde.

The prior art fails to address the longstanding unmet need in thefoundry industry for ester-cured alkaline phenolic no-bake bindersystems that will not only help foundries comply with OSHA standards forworker safety and health, but also improve the working environmentaround the systems by reducing the offensive odors and toxicityassociated with intolerable formaldehyde emission levels.

Accordingly, it would be advantageous to provide an ester-cured alkalinephenolic no-bake composition that reduces formaldehyde odor andemissions as compared to conventional ester-cured alkaline phenolicno-bake technologies, without sacrificing performance (i.e., tensilestrength) in the associated molds and cores or imparting nitrogenrelated defects in steel castings, as described herein.

SUMMARY OF THE INVENTION

Unexpectedly, in view of the foregoing challenges, it has been foundthat ester-cured alkaline phenolic no-bake binder systems having liquidester components that are modified with concentrations of resorcinolexhibit improved reduction of formaldehyde emissions without sacrificingperformance in foundry molds and cores that employ this technology.Reductions in formaldehyde are achieved due to the modification of theliquid ester with resorcinol, which functions as a scavenger by reactingwith formaldehyde during curing of the molds and cores.

In one preferred embodiment, a new modified ester-curative is provided,the modified ester-curative comprising an ester and resorcinol. Morespecifically, there is provided a modified ester-curative compositioncomprising: (a) an ester-curative; and (b) resorcinol; wherein theester-curative is selected from the group consisting of: (i) anester-curative comprising about 20% to about 30% glycerol triacetate byweight of the ester-curative, (ii) an ester-curative comprising about90% to about 100% glycerol triacetate by weight of the ester-curative,and (iii) an ester-curative comprising about 30% propylene carbonate byweight of the ester-curative and about 70% gamma butyrolactone by weightof the ester-curative; and wherein a ratio of (a) to (b) ranges fromabout 19:1 to about 99:1 by weight of the modified ester-curative.

In an alternative preferred embodiment, a new ester-cured alkalinephenolic no-bake composition comprising an alkaline phenolic resoleresin having a pH of at least 13 and a modified ester-curativecomprising an ester and resorcinol is provided. More specifically, thereis provided a composition comprising: a mixture comprised of anaggregate and an alkaline phenolic resole resin, the mixture combinedwith; a modified ester-curative comprised of (a) an ester-curative and(b) resorcinol; wherein a ratio of (a) to (b) ranges from about 19:1 toabout 99:1 by weight of the modified ester-curative; and wherein themodified ester-curative is configured to effect reduced emission offormaldehyde from the composition.

In yet another alternative preferred embodiment, a new method forforming foundry molds and cores having very low formaldehyde emissionsand excellent tensile strength characteristics is provided. Morespecifically, in this embodiment the method comprises the steps of: (a)combining an aggregate with an alkaline phenolic resole resin to form afirst admixture; (b) combining an ester-curative with resorcinol to forma modified ester-curative; (c) combining the first admixture with themodified ester-curative to form a second admixture; (d) placing thesecond admixture in a housing; and (e) allowing the second admixture tocure; wherein the ratio of ester-curative to the resorcinol ranges fromabout 19:1 to about 99:1 by weight of the modified ester-curative; andwherein the modified ester-curative is configured to effect reducedemission of formaldehyde from the second admixture.

An objective of the present invention is to provide a new and improvedester-cured alkaline phenolic no-bake binder composition that reducesformaldehyde emission during the curing process of foundry molds andcores, without sacrificing performance of the same.

A major advantage of the present invention is that it provides molds andcores having significantly lower emissions of formaldehyde during thecuring process than was heretofore obtainable with conventionalester-cured alkaline phenolic no-bake binder compositions and methods.

Another major advantage of the present invention is that it providesmolds and cores having the combined benefit of significantly loweremissions of formaldehyde during the curing process coupled withcommercially suitable tensile strength in the molds and cores than washeretofore obtainable with conventional ester-cured alkaline phenolicno-bake binder compositions and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

Not applicable.

DETAILED DESCRIPTION OF THE EMBODIMENTS

While the invention may be susceptible to embodiment in different forms,there is described herein in detail, specific preferred embodiments withthe understanding that the present disclosure is to be considered anexemplification of the principles of the invention, and is not intendedto limit the invention to that described herein.

In one preferred embodiment of the present invention, a composition isformed of a binder, an aggregate, an ester-curative, and resorcinol.

One preferred binder of the present invention is ALpHASET 9040 alkalinephenolic resole resin, made and sold by HA International LLC, Westmont,Ill. This resin is comprised of about 5% by weight to about 10% byweight sodium hydroxide, about 1% by weight to about 3% by weight ofurea, and less than about 0.3% by weight, formaldehyde. It has aviscosity of about 100 cPs, a solids content of about 47%, a specificgravity of about 1.23, a pH of about 13.0, a free phenol content ofabout 0.5%, a free formaldehyde content of about 0.25%, and a nitrogencontent of less than about 1%. It is ester-curable, preferably using aliquid ester. ALpHASET 9040 derives its alkalinity predominantly fromsodium hydroxide and thus it may be described as a sodium-based resin.It is contemplated, however, that other embodiments may include otheralkaline phenolic resole resins, such as a potassium based alkalineresin or a hybrid of sodium and potassium alkaline resins, as will beappreciated by those ordinary skill in the art.

One preferred aggregate of the present invention is clean, round grain,55 grain fineness number (GFN) silica sand. The aggregate materialscommonly used in the foundry industry include silica sand, constructionaggregate, quartz, chromite sand, zircon sand, olivine sand, or thelike. Reclaimed sand, that is sand that may have been previously bondedwith an ester cured alkaline phenolic resin binder, or other bindersystem, may also be used. Sand sold under the product designationF-5574, available from Badger Mining Corporation, Berlin, Wis., isuseful in making cores and molds and in testing the embodiments of thepresent invention. Likewise, sand sold under the product designationWedron 530, available from Wedron Silica, a division of FairmountMinerals, Wedron, Ill., is also useful. Sand sold under the productdesignation Nugent 480, available from Nugent Sand Company, Muskegon,Mich., may also be used. Where alkaline resoles are used in thecompositions and methods of the present invention, the sand type willaffect the strength development of the bound aggregate.

A preferred ester-curative, also referred to as a co-reactant, of thepresent invention accelerates the hardening of the resole resin and maybe introduced to the resole resin as a liquid. It is contemplated thatthe esters used in preparing the ester-curative compositions of thisinvention may be any of the esters commonly used to cure alkalinephenolic resole resins. Such esters include gamma-butyrolactone,triacetin, ethylene glycol diacetate, propyleneglycol diacetate,propylene carbonate, dimethyl succinate, dimethyl adipate, dimethylglutarate, glycerol mono-and diacetates and the like. Mixtures of theseester-curatives may also be used. It is further contemplated that otheresters, such as those described in U.S. Pat. Nos. 4,988,745 and5,036,116 may be used as well, and those patents are herein incorporatedby reference in their entirety.

One preferred ester-curative of the present invention is ALpHACURE 920,made and sold by HA International LLC, Westmont, Ill. Thisester-curative is comprised of about 90% by weight to about 100% byweight of glycerol triacetate, which is also known as triacetin. Thisester-curative has a relative density of about 1.154 g/cm³, a solubilityin water of about 6.1%, and it has a specific gravity of about 1.1.Further, this ester-curative contains no dibasic ester (DBE). It iscontemplated, however, that other embodiments may include otherester-curatives, as will be appreciated by those ordinary skill in theart.

Another preferred ester-curative of the present invention is ALpHACURE955N, made and sold by HA International LLC, Westmont, Ill. Thisester-curative is comprised of about 20% by weight to about 30% byweight of glycerol triacetate, and about 70% by weight to about 80% byweight of dibasic ester. This ester-curative has a relative density ofabout 1.107 g/cm³ and a dynamic viscosity of about 5 cPs. The preferreddibasic ester component of this ester-curative is comprised of about 10%by weight to about 25% by weight of dimethyl adipate, about 15% byweight to about 25% by weight of dimethyl succinate, and about 55% byweight to about 65% by weight of dimethyl glutarate. The greaterproportion of dibasic ester in ALpHACURE 955N as compared to that inALpHACURE 920 results in slower strip times, as indicated below in Table2B.

Yet another preferred ester-curative of the present invention is ablended combination of gamma butyrolactone and propylene carbonate. Thisester-curative is comprised of about 70% by weight of gammabutyrolactone and about 30% by weight of propylene carbonate. Gammabutyrolactone has a molecular weight of about 86 g/mol, a pH of about 4,and a relative density of about 1.12 g/cm³. Propylene carbonate has amolecular weight of about 102.09 g/mol, a specific gravity of about1.205 and a relative density of about 1.21 g/cm³.

Resorcinol is comprised of about 99.7% by weight of resorcinol, about0.2% by weight of moisture, and about 0.1% by weight of phenol.Resorcinol itself is a benzenediol having a molecular weight of about110.1 g/mol and a relative density of about 1.28 g/cm³. In preferredembodiments of the present invention, it has been found that amodification with resorcinol of the ester-curative component of theester-cured alkaline phenolic no-bake binder systems described hereinresults in an unexpected and desirable reduction in formaldehydeemission and odor from the molds and cores, without sacrificing tensilestrength of the same.

A stoichiometric amount of ester is essential to co-react with theresin. The use of high and low levels of ester can lead to castingdefects. While the level of resorcinol in the ester results informaldehyde reduction, too much will detract from the curing speed ofthe molds and core, and/or require higher ester levels to maintainstoichiometry. 1 to 5% by weight of resorcinol in the modified ester isthe preferred amount. Additionally, preferred embodiments of the presentinvention which include pure resorcinol, as opposed to resorcinol pitch,are advantageous because pure resorcinol is more potent than resorcinolpitch with respect to reactivity with unreacted formaldehyde. Therefore,less resorcinol by weight may be used in the preferred embodiments ofthe present invention as compared to greater amounts of resorcinol pitchthat would otherwise be required to achieve the formaldehyde emissionreductions and strip times provided by the systems and methods of thepresent invention. Moreover, whereas the odor of pure resorcinol isfaint, the odor of resorcinol pitch is strong, such that the use ofresorcinol pitch would be inapposite to one of the underlying purposesof the present invention which is to reduce the exposure of individualsto offensive odors during the manufacture of foundry binder systems.

Methodology

Generally, when an admixture is to be cured according to a no-bakeprocess, the ester-curative is added in liquid form to the aggregatematerial with the phenolic resole resin component. The admixture is thenshaped and simply permitted to cure until reaction between thecomponents is substantially complete, thus forming a shaped product suchas a foundry core or mold. It is contemplated, however, that otheradmixing methods may be used, as will be appreciated by those ordinaryskill in the art. Moreover, it is contemplated that admixtures of thepresent invention may be allowed to cure in any housing suitable for usewith ester-cured phenolic binder systems, including pattern molds andcore boxes.

Consequently, by so proceeding with an admixture of foundry sand and abinding amount of the phenolic resole resin, including resorcinolcomponents in the ester-curative, there is formed a foundry core or moldcomprising foundry sand and a binding amount of a binder compositioncomprising the reaction product of the phenolic resole resin, theresorcinol component, and the ester-curative. Ester-curatives combinedwith resorcinol as recited herein are referred to as modifiedester-curatives.

As further described herein, ALpHASET 9040 was tested in conjunctionwith various resorcinol modified esters. The formaldehyde measurementswere made in each instance using EPA method 316, which is incorporatedby reference herein in its entirety. Sand tests were also performed toshow any effect on tensile strength. Unless otherwise indicated, alltest samples of the present invention to be analyzed for formaldehydeemission were prepared using the following process.

Formaldehyde Collection and Analysis

All samples were prepared using a Hobart Kitchen Aid Mixer. 3000 g ofthe 55 GFN sand was weighed in a mixing bowl. 1.5% (45 grams) by weightbased on sand (BOS) of ALpHASET 9040 was weighed, added to the sand, andmixed for 60 seconds. 25% (11.25 grams) of modified ester-curative byweight based on binder (BOB) was added to the coated sand and mixed foran additional 40 seconds. At the end of mixing, the coated sand samplewas immediately placed in a test box and tamped down. The test box wasthen closed with a lid and formaldehyde was drawn into samples from thebox for 20 minutes. The samples were then analyzed by an outside lab forformaldehyde using the analytical procedures of EPA Method 316.

Tensile Strength Test

Unless otherwise indicated, all foundry cores of the present inventionto be analyzed for tensile strength were prepared using the followingprocess. HA International's standard sand tensile strength testprocedure was used. 3000 g of the 55 GFN sand was weighed in a mixingbowl. 1.5% (45 grams) by weight BOS of ALpHASET 9040 was added to thesand and mixed for 60 seconds. 25% of modified ester-curative (11.25grams) by weight BOB was added to the coated sand and mixed for afurther 40 seconds. The mixed sand was packed into a Dietert 696 corebox, which is standard tooling for making cores. Part of the mixed sandwas lightly packed into a cup, and a tongue depressor was placed in thetop of the mixed sand to check for strip time. When the tongue depressorwas hard to push down, it was near strip time. Once 15-18 pounds persquare inch (psi) of mold surface strength when subjected to the forceof a spring loaded penetrometer was achieved, the cores were removedfrom the core box. (The length of time between the mixing of all corecomponents, i.e., after addition of the ester-curative, and achievementof the aforementioned core surface strength sufficient to allow thecores to be removed from the core box is the strip time.) The strip timewas recorded and the test cores were broken at various time intervalsafter the cores was made. The cores were stored in an open laboratoryenvironment, at ambient temperatures, until tested. Tensile strengthmeasurements were made as described below. Average values for 3 to 4tensile strength measurements were recorded.

Tensile strengths of the cores prepared as noted above were determinedusing a Thwing-Albert Tensile Tester (Philadelphia, Pa.). This deviceconsists of jaws that accommodate the ends of a “dog-bone-shaped” testcore. A load is then applied to each end of the test core as the jawsare moved away from each other. The application of an increasing loadcontinues until the test core breaks. The load at this point is termedthe tensile strength, and it has units of psi.

EXAMPLES Example 1 Effect of Adding Resorcinol to ALpHACURE 920 in anEster-Cured Alkaline Phenolic No-Bake Binder Composition

In this example, 1%, 3%, and 5% (by weight) of resorcinol was dissolvedin 99%, 97%, and 95% (by weight) of ALpHACURE 920, respectively. Samplesand cores were made, as described above. The formaldehyde emissionsmeasurements were made using EPA Method 316 and the results of themeasurements are provided in Table 1A below.

TABLE 1A Reduction of Formaldehyde Emission in Ester-Cured AlkalinePhenolic No-Bake Binder Composition Combining ALpHACURE 920 andResorcinol Sample Modified Ester-Curative Formaldehyde Reduction, NumberComposition, wt % Emitted, ppm % Control 100% ALpHACURE 1.302 n/a Sample920 Test 99% ALpHACURE 0.945 27.4 Sample 920 + 1% 1 Resorcinol Test 97%ALpHACURE 0.603 53.7 Sample 920 + 3% 2 Resorcinol Test 95% ALpHACURE0.298 77.1 Sample 920 + 5% 3 Resorcinol

As the results of Table 1A illustrate, the use of the modifiedester-curative composition of the present invention in ester-curedalkaline phenolic no-bake binder systems results in unexpected andcompelling reductions in formaldehyde emissions from the systems, namelyfoundry molds and cores.

Additionally, the tensile strength of cores formed under Example 1 weretested using a Thwing-Albert Tensile Tester, as described above. Theresults of the tests are provided in Table 1B below.

TABLE 1B Sustained Tensile Strength of Ester-Cured Alkaline PhenolicNo-Bake Binder Composition Having Reduced of Formaldehyde Emission andCombining ALpHACURE 920 and Resorcinol Tensile Tensile Tensile Modified“Intermediate” Strength Strength Strength Ester-Curative Strip at at at24 Core Composition, Time, 1 Hour, 2 Hours, Hours, Number wt % minutespsi psi psi Control 100% 16.5 67 74 139 Core ALpHACURE 920 Test 99% 17.662 82 122 Core ALpHACURE 1 920 + 1% Resorcinol Test 97% 18.8 61 85 134Core ALpHACURE 2 920 + 3% Resorcinol Test 95% 19.3 62 83 145 CoreALpHACURE 3 920 + 5% Resorcinol

As the results of Table 1B illustrate, the use of the modifiedester-curative composition of the present invention in ester-curedalkaline phenolic no-bake binder systems has a limited effect onintermediate strip times and no significant effect on tensile strengthof the systems, including foundry molds and cores.

Example 2 Effect of Adding Resorcinol to ALpHACURE 955N in anEster-Cured Alkaline Phenolic No-Bake Binder Composition

In this example, 5% (by weight) of resorcinol was dissolved in 95% (byweight) of ALpHACURE 955N. Samples and cores were made, as describedabove. The formaldehyde emissions measurements were made using EPAMethod 316 and the results of the measurements are provided in Table 2Abelow.

TABLE 2A Reduction of Formaldehyde Emission in Ester-Cured AlkalinePhenolic No- Bake Binder Composition Combining ALpHACURE 955N andResorcinol Sample Modified Ester-Curative Formaldehyde Reduction, NumberComposition, wt % Emitted, ppm % Control 100% ALpHACURE 955N 0.527 n/aSample Test Sample 95% ALpHACURE 955N + 0.055 89.6 1 5% Resorcinol

As the results of Table 2A illustrate, the use of the modifiedester-curative composition of the present invention in ester-curedalkaline phenolic no-bake binder systems results in unexpected andcompelling reductions in formaldehyde emissions from the systems,including the foundry molds and cores.

Additionally, the tensile strength of cores formed under Example 2 weretested using a Thwing-Albert Tensile Tester, as described above. Theresults of the tests are provided in Table 2B below.

TABLE 2B Sustained Tensile Strength of Ester-Cured Alkaline PhenolicNo-Bake Binder Composition Having Reduced of Formaldehyde Emission andCombining ALpHACURE 955N and Resorcinol Modified Ester- “Slow” TensileTensile Tensile Curative Strip Strength Strength Strength CoreComposition, Time, at 2 at 4 at 72 Number wt % minutes Hours, psi Hours,psi Hours, psi Control 100% 66 40 70 105 Core ALpHACURE 955N Test 95%75.5 49 77 128 Core 1 ALpHACURE 955N + 5% Resorcinol

As the results of Table 2B illustrate, the use of the modifiedester-curative composition of the present invention in ester-curedalkaline phenolic no-bake binder systems has a limited effect on slowstrip times and no significant effect on tensile strength of thesystems, including the foundry molds and cores.

Example 3 Effect of Adding Resorcinol to an Ester Blend Comprised ofGamma Butyrolactone and Propylene Carbonate in an Ester-Cured AlkalinePhenolic No-Bake Binder Composition

In this example, 5% (by weight) of resorcinol was dissolved in 95% (byweight) of an ester blend comprised of 70% (by weight) of gammabutyrolactone and 30% (by weight) of propylene carbonate. Samples andcores were made, as described above. The formaldehyde emissionsmeasurements were made using EPA Method 316 and the results of themeasurements are provided in Table 3A below.

TABLE 3A Reduction of Formaldehyde Emission in Ester-Cured AlkalinePhenolic No-Bake Binder Composition Combining Blended Ester andResorcinol Sample Modified Ester-Curative Formaldehyde Reduction, NumberComposition, wt % Emitted, ppm % Control 70% gamma butyrolactone 4.149n/a Sample and 30% propylene carbonate Test 95% of (70% gamma 2.127 48.7Sample butyrolactone + 30% propylene 1 carbonate) + 5% Resorcinol

As the results of Table 3A illustrate, the use of the modifiedester-curative composition of the present invention in ester-curedalkaline phenolic no-bake binder systems results in unexpected andcompelling reductions in formaldehyde emissions from the systems,including the foundry molds and cores.

Additionally, the tensile strength of the cores formed under Example 3were tested using a Thwing-Albert Tensile Tester, as described above.The results of the tests are provided in Table 3B below.

TABLE 3B Sustained Tensile Strength of Ester-Cured Alkaline PhenolicNo-Bake Binder Composition Having Reduced of Formaldehyde Emission andCombining Blended Ester and Resorcinol Core Modified Ester-Curative“Fast” Strip Tensile Strength at Tensile Strength at 2 NumberComposition, wt % Time, minutes 1 Hour, psi Hours, psi Control 70% gamma2.5 63 66 Core butyrolactone and 30% propylene carbonate Test 95% of(70% gamma 2.8 69 79 Core 1 butyrolactone + 30% propylene carbonate) +5% Resorcinol

As the results of Table 3B illustrate, the use of the modifiedester-curative composition of the present invention in ester-curedalkaline phenolic no-bake binder systems has a limited effect on faststrip times and no significant effect on tensile strength of thesystems, including the foundry molds and cores.

While the invention has been described with specific embodiments, manyalternatives, modifications, and variations will be apparent to thoseskilled in the art in light of the foregoing description. Accordingly,the present invention is intended to include all such alternatives,modifications, and variations set forth within the spirit and scope ofthe appended claims.

What is claimed is:
 1. A modified ester-curative composition comprising:(a) an ester-curative; and (b) resorcinol; wherein the ester-curative isat least one member of the group consisting of: (i) an ester-curativecomprising about 20% to about 30% glycerol triacetate by weight of theester-curative, (ii) an ester-curative comprising about 90% to about100% glycerol triacetate by weight of the ester-curative, (iii) anester-curative comprising about 30% propylene carbonate by weight of theester-curative and about 70% gamma butyrolactone by weight of theester-curative, and (iv) an ester-curative comprising about 70% to about80% dibasic ester by weight of the ester-curative; and wherein a ratioof (a) to (b) ranges from about 19:1 to about 99:1 by weight of themodified ester-curative.
 2. The composition of claim 1, wherein theester-curative is about 20% to about 30% glycerol triacetate by weightof the ester-curative and the ratio is about 19:1.
 3. The composition ofclaim 1, wherein the ester-curative is about 90% to about 100% glyceroltriacetate by weight of the ester-curative and the ratio is about 32:1.4. The composition of claim 1, wherein the ester-curative is about 30%propylene carbonate by weight of the ester-curative and about 70% gammabutyrolactone by weight of the ester-curative and the ratio is about19:1.
 5. The composition of claim 1, wherein the ester-curative is about70% to about 80% dibasic ester by weight of the ester-curative, and theratio is about 19:1.
 6. The composition of claim 1, the ester-curativeis at least one member of the group consisting of (i) an ester-curativecomprising about 90% to about 100% glycerol triacetate by weight of theester-curative, and (ii) an ester-curative comprising about 30%propylene carbonate by weight of the ester-curative and about 70% gammabutyrolactone by weight of the ester-curative.
 7. A foundry compositioncomprising: a mixture comprised of an aggregate and an alkaline phenolicresole resin, the mixture combined with; a modified ester-curativecomprised of (a) an ester-curative and (b) resorcinol; wherein a ratioof (a) to (b) ranges from about 19:1 to about 99:1 by weight of themodified ester-curative; and wherein the modified ester-curative isconfigured to effect reduced emission of formaldehyde from thecomposition.
 8. The composition of claim 7, wherein the ratio is about32:1.
 9. The composition of claim 7, wherein the resin comprises about5% to about 10% sodium hydroxide by weight of the resin.
 10. Thecomposition of claim 7, wherein the ester-curative comprises about 20%to about 30% glycerol triacetate by weight of the ester-curative and theratio is about 19:1.
 11. The composition of claim 7, wherein theester-curative comprises about 70% to about 80% dibasic ester by weightof the ester-curative and the ratio is about 19:1.
 12. The compositionof claim 7, wherein the ester-curative comprises about 90% to about 100%glycerol triacetate by weight of the ester-curative and the ratio isabout 32:1.
 13. The composition of claim 7, wherein the ester-curativecomprises about 30% propylene carbonate by weight of the ester-curativeand about 70% gamma butyrolactone by weight of the ester-curative andthe ratio is about 19:1.
 14. A method for forming foundry molds andcores comprising the steps of: (a) combining an aggregate with analkaline phenolic resole resin to form a first admixture; (b) combiningan ester-curative with resorcinol to form a modified ester-curative; (c)combining the first admixture with the modified ester-curative to form asecond admixture; (d) placing the second admixture in a housing; and (e)allowing the second admixture to cure; wherein the ratio ofester-curative to the resorcinol ranges from about 19:1 to about 99:1 byweight of the modified ester-curative; and wherein the modifiedester-curative is configured to effect reduced emission of formaldehydefrom the second admixture.
 15. The method of claim 14, wherein the ratiois about 32:1.
 16. The method of claim 14, wherein the resin comprisesabout 5% to about 10% sodium hydroxide by weight of the resin.
 17. Themethod of claim 14, wherein the ester-curative comprises about 20% toabout 30% glycerol triacetate by weight of the ester-curative and theratio is about 19:1.
 18. The method of claim 14, wherein theester-curative comprises about 90% to about 100% glycerol triacetate byweight of the ester-curative and the ratio is about 32:1.
 19. The methodof claim 14, wherein the ester-curative comprises about 70% to about 80%dibasic ester by weight of the ester-curative and the ratio is about19:1.
 20. The method of claim 14, wherein the ester-curative comprisesabout 30% propylene carbonate by weight of the ester-curative and about70% gamma butyrolactone by weight of the ester-curative and the range isabout 19:1.